"Simulated niche partitioning by bacteria"
Bacterial evolution is simulated for continuous growth conditions using a population balance method, in which net bacterial growth and nutrient uptake are expressed with differential equations. Bacterial metabolism for the simulation is simplified from a highly complex biochemical network to three different designs that are composed of a simple module. It is based on the Michaelis-Menten reaction scheme and obeys thermodynamic constraints. When the simulated metabolic network has two modules in parallel that metabolize different substrates, and is grown with both substrates, evolution leads to coexisting bacterial populations that specialize on different nutrients. Upon increasing the bioreactor flow rate, the bacterial community undergoes a rapid transition to a single generalist population that consumes both substrates, leading to the possibility of experimental observation. This transition is reversible and hysteretic. In a different design, the modules are placed in series and the cell permeability to an intermediate metabolite is allowed to evolve. Again, it is possible to achieve stable coexisting populations: one population metabolizes the substrate to the intermediate metabolite while the other consumes the intermediate metabolite. Community matrices and stability criteria are discussed.